The present invention is directed to an improved hydrostatic controller for controlling fluid flow to a device such as a steering cylinder of a vehicle, which steering cylinder is actuated to effect powered steering of the vehicle. Hydrostatic controllers for controlling the flow of fluid to a steering cylinder of a vehicle to effect proper steering in response to rotation of the steering wheel of a vehicle are known. As is well known in the art, these structures include a gerotor gearset for metering the flow of fluid to the steering cylinder so that the steering of the vehicle is accomplished in the proper follow-up manner to the turning of the steering wheel.
Typically, these known hydrostatic controllers include a valve mechanism which, on turning of the steering wheel, ports fluid to the gerotor gearset and then receives metered fluid from the gerotor gearset portion the metered fluid to the steering cylinder. These mechanisms include a valve spool which is moved, upon turning of the steering wheel, to effect the porting of the fluid. In addition, these devices, as is known in the art, include a commutator valve arrangement which is associated with the gerotor gearset for controlling the flow of fluid into the expanding pockets of the gerotor gearset and from the contracting pockets of the gerotor gearset. The commutator valve arrangement in such structures may take a variety of different forms, and, in general, includes a number of valve parts of relatively complex design functionally interposed between the valve spool and the gerotor gearset.
Known controllers, in view of the fact that a valve spool is utilized for purposes of control of fluid flow and a separate commutator valve arrangement is utilized, require a substantial number of parts and many such controllers are of a substantial length. In addition, the component parts of the known controllers are relatively complex, all of which makes the controller somewhat difficult to assemble. In addition, the ratio of accepted versus reject controllers can be fairly high upon inspection. Moreover, small tolerances are required in the known controllers to ensure stable operation of the controllers on the vehicle. Furthermore, in the known hydrostatic controllers, the shaft seal which provides a fluid seal between the shaft connected with the steering wheel and the control valve is exposed to the highest pressure in the controller and this accordingly has created problems in terms of the proper construction and efficient construction of a good shaft seal.